What version of Premiere Elements and on what computer operating system? Are you working with some version of Premiere Pro? If so, you have posted in the wrong forum. Your thread has been posted to the Adobe Premiere Elements Forum.
Assuming that you have some version of Premiere Elements.....
Where is this "original soundtrack" coming from and what are its properties?
Is this a file that you are importing with its fade/volume at the end that you like, and you feel that "Premiere" is messing up fade/volume once it is dragged to your Timeline?
If this is an imported file, rather than music supplied by the program, have you applied any adjusts/effects to it?
Let us start here and then decide what next.
Premiere Elements 13,, Windows 8, the file is a wave file from Adobe Audition
I think it may have something to do with Windows 8 and the audio system which is Beatsaudio because it does this with just wave and mp3 files also that are not in Premiere. Although one time I added a wave file to the computer and listened to it on windows media player. It did not adjust the ending. I added it to a Premiere project and the ending spiked up to keep the volume constant. Then when I listened to the song again on windows player it spiked up so I think Premiere is activating something Thanks for responding anyway.
Thank you for the supplemental information for your question.
I do not know that Premiere Elements (any version) is "activating something" for your imported audio. I do know that any audio (your own or Adobe audio) goes through a conformed process. You will find the conformed audio files (cfa and peks sets) in the Media Cache Files Folder in the Adobe Folder.
If I took one of my files into a Premiere Elements project, this particular audio's properties would include
Source Audio Format 44100 Hz - compressed - stereo
Project Audio 44100 Hz - 32 bit floating point - stereo
If you import your audio into Premiere Elements 13 Expert workspace, open Project Assets, right click the thumbnail for the audio file there, and select Properties, what do you see for Source Audio and Project Audio for your file?
Also, after you import your audio into the project's Expert workspace and drag it to the soundtrack, if you go to Adjust Tab/Adjustments Palette/ do you see any audio related panels with a green dot to the right of the panel?
Are you dealing with audio with or without the SmartSound or Music Score concept where the file is designed so that altering its duration does not alter the arrangement?